The King

The King is allowed to move into check or ignore checks.

The King can be captured.

Checkmating the King wins.

Moving the King into a checkmated position, will make you lose the
game if your opponent's move does not release your King from checkmate,
i.e. the game does not end immediately, rather, it may or may not end after
your opponent has replied.

In particular, your King can legally check or capture your opponent's
King, or even deliver checkmate if your King is guarded!

Promotion

Promotion zone is at the last three rows, consisting of only nine squares.

A promotable piece may promote upon entering or moving within the zone;
it may not promote upon leaving or moving outside the zone.

Promoting is optional.

Promoting the King instantly wins!

The King cannot promote when moving into check, but it can promote
when moving into checkmate, in which case the player still wins: this rule takes
precedence over checkmate. This should only happen when the King flees
from check.

A Ferz promotes to chess Bishop.

A Wazir promotes to chess Rook.

A Knight promotes to a Paladin, that moves like a Knight or King.

A Bishop promotes to a Horse, that moves like Bishop or Wazir.

A Rook promotes to a Dragon, that moves like Rook or Ferz.

A Paladin promotes to Castle, that combines Dababba, Knight, and Alfil.

A Horse promotes to a Tiger, that moves like Horse or Knight.

A Dragon promotes to a Lion, that moves like Dragon or Knight.

A Castle promotes to an Elephant, that combines Castle, Rook, and Bishop.

Neither a Tiger, a Lion, nor an Elephant promotes.

Drops

Captured piece is held in-hand by the captor.

A piece may only be held in-hand for at most three turns, thereafter
it must be re-dropped. Example: White captures something in his 6th turn,
he must drop this piece on his 7th, 8th, or 9th turn.

When you drop you also make a move. Dropping is not instead of a
move.

Dropping takes place after the move.

You may drop multiple pieces in the same turn.

You may not drop the piece you have just captured in the same turn.

Pieces in-hand may be dropped into any empty square.

A captured promoted piece reverts back to Ferz, Wazir, Knight, or King.

You may not change the type of the piece, so:

Ferzes, Bishops, Horses, and Tigers are dropped as Ferzes,

Wazirs, Rooks, Dragons, and Lions are dropped as Wazirs,

Knights, Paladins, Castles, and Elephants are dropped as Knights,

the King is dropped as a King.

Whenever there are two Ferzes, a Ferz and a Bishop, or two Bishops,
owned by the same player on board, they must be on different-colored squares.
If you capture a Horse while the opponent already has a Bishop on a white
square, you may only drop the Ferz on a black square. If you have two Ferzes
in hand you can drop them both in the same turn, but one must be on a white
square and the other on a black square.

A dropped piece does not change its color, unlike Shogi.

A King can be dropped in a square where checkmate is already arranged.
You can win by dropping your opponent's King in your hand right in the
checkmate net you have set up.

Sources of Inspirations

The King. This is my original idea: checkmate wins, but checks can be
ignored.

Promotion. This is from Shogi, however
since the pieces promote multiple times it is necessary to forbid the promotion
upon leaving the zone.

Promoting the King wins. This is a variation of a rule in many other
chess variants utilizing a "thorne square" where the King, upon
its arrival on his counterpart's starting position, wins the game. An example
is from Drawless Chess. Since
there are nine squares, instead of one, I found the rule "the King
cannot promote when moving into check" necessary.

Drops, this is another Shogi element. However,
that the piece does not change its color, is my idea. It is therefore needed
to introduce the three-moves countdown rule, as otherwise players will
never drop a captured piece back. Why three, because it is half the number
of non-King pieces in each army.

That dropping pieces does not take your move, is just my idea to encourage
captures.

That Ferzes and Bishops must be on different-colored squares, is another
of my idea after reading the Bishops Conversion
Rule found in some games.

King drop mated, this is another of my original idea, that seems to
work well with the three-moves rule.